First posting: Kappa Draconis

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Alun Halsey
Posts: 20
Joined: Fri Jan 19, 2018 10:53 am

First posting: Kappa Draconis

Post by Alun Halsey »

Hi,
First time posting on this forum, back on night of 15/02/18 I had a go at Kappa Dra using my C9.25 and Lhires III with 15um slit,camera is Atik 314L.
Captured four 120sec images which were stacked,dark,flat and flat dark subtracted in BASS. Calibrated using three neon lines of Lhires calibration lamp,no instrument response correction administered.
Kappa Dra.jpg
Kappa Dra.jpg (45.03 KiB) Viewed 4295 times

Regards
Alun
LHires III + SX Trius pro 694,ALPY 600 + SX Trius pro 825,Star analyser 100,C9.25,Esprit 150 ED Apo, Evostar 72ED with Sol'Ex SHG. Mesu 200 Mk1
Robin Leadbeater
Posts: 1926
Joined: Mon Sep 26, 2011 4:41 pm
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Re: First posting: Kappa Draconis

Post by Robin Leadbeater »

Hi Alun,

If you do not have a reference star spectrum to do an instrument response the continuum shape is meaningless so it is a good idea to rectify the spectrum (ie flatten it by normalising using a fit to the continuum). In this case a straight line fit to the continuum well away from the H alpha line would probably work OK. You can then set the appropriate flag in the (BeSS standard) fits header ready for submission to databases.
(Actually I am bit surprised at the amount of slope in the continuum though. Perhaps it is an effect of BASS but with ISIS, if a flat correction has been done with a halogen lamp, the continuum is an almost horizontal straight line over this short wavelength interval as ISIS compensates for the approximate black body curve of a halogen lamp)

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk
Robin Leadbeater
Posts: 1926
Joined: Mon Sep 26, 2011 4:41 pm
Contact:

Re: First posting: Kappa Draconis

Post by Robin Leadbeater »

Also your continuum looks rather noisy for such a bright target. A good minimum SNR to aim for on bright targets is an SNR >100. You could increase exposure time but it could also be to do with the narrow 15um slit. Unless your seeing is exceptionally good you could be losing a lot of light. (15um corresponds to just 1.3 arcsec with your scope) 23um (or even 35um though with some loss of resolution relative to the LHIRES design figure of R~17000 at H alpha) would give you more signal. I used to run 23um with my 8 inch f10 and now run 35um with my C11

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk
Alun Halsey
Posts: 20
Joined: Fri Jan 19, 2018 10:53 am

Re: First posting: Kappa Draconis

Post by Alun Halsey »

Hi Robin,

Thank you for the advice. I use the internal lamp of the Lhires III to take my flats,could be possible I didn't take them correctly (too short an exposure).
I used the 15um slit as Kappa Dra was the last target of the night after I'd earlier been concentrating on 28 Tau. I use mainly use BASS for all my calibrating
but just recently downloaded a copy of ISIS and am trying to get used to the software. I input the Kappa Dra data into ISIS and the result was identical to that produced by BASS. Had another go at this star last night using the 23um slit and 600sec exposures,will post results when calibrated.

Best Regards
Alun
LHires III + SX Trius pro 694,ALPY 600 + SX Trius pro 825,Star analyser 100,C9.25,Esprit 150 ED Apo, Evostar 72ED with Sol'Ex SHG. Mesu 200 Mk1
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